1. Field of the Invention
The present invention relates generally to the manufacture of manifolds for automobile cooling systems, and more particularly, to a system, method, and apparatus for manufacturing a manifold for a condenser or heat exchanger.
2. Discussion of the Related Art
Automotive climate control systems are well known in the art. Automobiles typically utilize climate control systems to absorb and dissipate heat from inside a passenger cabin to the outside of the automobile. In such systems, a manifold block or a direct pipe connects the condenser manifold to both a compressor and an expansion valve. The manifold block connects the compressor to the condenser and the condenser to an evaporator, so that refrigerant can flow between them. Refrigerant at high temperature and high pressure in vapor form flows through the pipes from the compressor to the condenser, via the condenser manifold. In the condenser, the high temperature and high pressure refrigerant in vapor form is condensed to form refrigerant in high temperature high pressure liquid form. Then, the liquid is passed through an expansion valve. The valve restricts the flow of the refrigerant, lowering the pressure of the liquid and forming low pressure low temperature liquid. This liquid refrigerant is then passed through the evaporator, where heat from the passenger cabin is absorbed as the refrigerant liquid evaporates. The resulting low pressure low temperature refrigerant flows to the compressor, which pressurizes the refrigerant to form high pressure high temperature vapor, repeating the process.
There are three basic methods currently used to manufacture condenser of heat exchanger manifolds in so-called tube-and-fin condensers. The first method involves cold forging. In the cold forging method, a metal used to form the manifold is melted and is molded into a basic shaped via an extrusion process. After the basic shape of the manifold is formed, the metal is cooled to ready the part for the next operation. The basic shape of the manifold is formed through the extrusion process. During the extrusion process, excess material surrounds what is to become the individual risers of the manifold. The extra material is removed via a machining process, creating a shape out of solid metal that looks like a short, solid riser. This basic shape is then cold-forged to create the final riser shape. Once the riser shape is formed, the tip of the risers are machined out or punched out via a press to form a hole.
There are drawbacks to the first method, however. The machining process often is very time-consuming and can be expensive and cumbersome because each of the risers needs to be machined prior to the cold-forging process. Also, because the cold forging step involves the application of tremendous pressure to the metal forming the manifold, manifolds are often damaged and then have to be scrapped. The tremendous pressure required for cold-forging process also affects the life of dies used in the cold-forging process. Due to the tremendous pressure, dies are prone to cracks and breakage. The die breakage is often unpredictable, and is a routine problem in the cold-forging process.
The second method of manufacturing manifolds involves machining the entire manifold directly from a block of metal. However, it is extremely wasteful to machine a manifold from an entire block of metal because a large portion of the metal that is machined off must be scrapped, since it cannot be used to form another manifold. Also, as mentioned above, the machining process is very time-consuming and can be expensive and cumbersome.
The third method of manufacturing manifolds is stamping. In a stamping process, a large die is used and a metal used to form the manifold is gradually bent into the shape of the manifold. A basic sheet metal is often used as the source metal to form the manifold. The sheet metal is then bent in a number of stages. Stamping requires a large amount of pressure to bend the metal into the shape of the manifold. However, unlike cold forging, the pressure is applied gradually over multiple stages rather than all at once. Typical dies in the art can use 20-30 stages to form the manifold.
The typical stamping process involves using one die to form the entire manifold. The various portions of the manifold are usually formed in different stages within the die. The risers can be formed via a series of stages, then the tubular shape of the manifold tanks can be formed, and finally the baffles can be formed. However, since a single die is used, the partially completed part cannot be cleaned of scraps between the time at which the riser are formed and the time at which the tubular shape of the tanks is formed. For example, if grease, dirt, or any miscellaneous scrap gets caught inside the formed tank or risers, an operator generally cannot clean out the impurity until after the entire manifold is formed. Moreover, it is very difficult to detect whether scrap is trapped in the manifold once the part takes the shape of the finished product. Accordingly, the scrap can go undetected until it is coupled to a condenser, at which point the performance of the condenser can be diminished. Once the part is in the shape of a finished product, even if a scrap is detected within the part, there is no practical means of extracting the scrap from within the finished product, resulting in disposal of the affected part. Additionally, when the manifold is in the final shape with the baffles and end crimp closures, the degreasing process becomes very difficult. When the sheet metal is being stamped into the manifold shape, heavy work oil needs to be utilized. This oil can easily get trapped where the sheet metal is pressed together to form a particular shape. With the manifolds, where the next operation is the brazing process, having any trace of heavy work oil is detrimental to the latter operation.
Also, the use of a single die can result in large time consumption. For example, if the die is currently set to produce manifolds of a particular length, it can take several hours to reset the die to produce a different manifold length. Additionally, if a die is designed to manufacture several part models, which typically is the case, there is additional part-specific setup involved. Moreover, since so many stages are undertaken by a single die, a very large press must be utilized to stamp out the manifold. The large press results in large operating costs and initial investment costs. Accordingly, because a supplier of manifolds is often under large time-pressure to deliver completed manifolds, the supplier typically has to maintain a large stock of different-sized manifolds in case they are needed. If a manufacturer utilizing one die to manufacture several different models, opts to not maintain inventory of finished parts, it must go through time-consuming die changeover many times to manufacture several different models. Additionally, for every down time, as a result of die changeover, no production can take place. An alternative to eliminate the down time is to manufacture a duplicate die. However, large complex progressive dies are quite expensive to manufacture, and thus duplicating dies present a costly alternative. Moreover, if 2 dies are to be operated simultaneously, a significant capital investment is necessary, since at least 2 large progressive die presses are required.